WJEC A Level Physics
WJEC A Level Physics Unit 4: Fields and Options Exam Questions
Free WJEC A Level Physics exam questions for Unit 4: Fields and Options, with a mark scheme for every pack. Covers capacitors, electric and gravitational fields, orbits and dark matter, magnetic fields, electromagnetic induction and the chosen option.
Unit 4: Fields and Options exam questions
9 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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A-Level Physics Flashcards for 2027 Onwards
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About WJEC A Level Physics Unit 4: Fields and Options
Unit 4 of WJEC A Level Physics, Fields and Options, is the second A2 unit. It covers capacitance and exponential discharge, electrostatic and gravitational fields, orbits and the wider universe including Kepler's laws, dark matter and Hubble's law, magnetic fields and forces on currents and moving charges, and electromagnetic induction. It also contains one option taught by your centre: Alternating Currents, Medical Physics, The Physics of Sports, or Energy and the Environment. Examiners test capacitor charge and discharge, field and potential calculations, orbital periods, force on a conductor, Faraday's and Lenz's laws and the option content.
What you need to know
- 4.1 C = Q / V, parallel plate capacitors C = epsilon0 A / d, energy U = 1/2 QV, capacitors in series and parallel, and exponential charge and discharge with time constant RC.
- 4.2 Coulomb's law and Newton's law of gravitation, field strength, potential, equipotentials, and comparing electric and gravitational fields.
- 4.3 Kepler's laws, circular orbits with T^2 proportional to r^3, escape velocity, the Doppler effect to find orbital speeds, galaxy rotation curves and dark matter, and Hubble's law.
- 4.4 Magnetic flux density, F = BIl sin(theta), F = Bqv sin(theta), fields around wires and solenoids, the Hall effect, and charged particles in fields.
- 4.5 Magnetic flux and flux linkage, Faraday's law, Lenz's law, and induced EMF in moving conductors and rotating coils.
- Options One option: Alternating Currents, Medical Physics, The Physics of Sports, or Energy and the Environment, assessed in the same exam.
Common mistakes in Unit 4: Fields and Options
- Saying capacitors in series add like resistors in series. Capacitances in parallel add; in series, add the reciprocals.
- Using the satellite's height above the surface as r. Orbital radius is measured from the centre of the planet, so add the planet's radius.
- Forgetting the negative sign in gravitational potential. Gravitational potential is negative and increases towards zero at infinity.
- Applying F = BIl when the wire is parallel to the field. The force is zero when the current is parallel to B; use F = BIl sin(theta).
- Thinking an EMF is induced only when a magnet is inside a coil. An EMF is induced whenever the flux linkage changes, including when the magnet moves away.
Try three Unit 4: Fields and Options exam-style questions
1. A satellite orbits Earth at a radius of 7.0 x 10^6 m. Earth's mass is 6.0 x 10^24 kg. Calculate the orbital period. (3 marks)
Show the mark scheme answer
T = 2 pi root(r^3 / GM); r^3 / GM = 3.43 x 10^20 / (6.67 x 10^-11 x 6.0 x 10^24) = 8.57 x 10^5 s2; T = 2 pi x 926 = 5.8 x 10^3 s.
2. A 0.15 m wire carrying 3.0 A lies perpendicular to a 0.20 T field. Calculate the force on it. (1 mark)
Show the mark scheme answer
F = BIl = 0.20 x 3.0 x 0.15 = 0.090 N.
3. State Lenz's law and explain how it relates to conservation of energy. (3 marks)
Show the mark scheme answer
The induced EMF acts to oppose the change in flux that causes it; so work must be done to move a magnet or conductor against the opposing force; this work is converted to electrical energy, so energy is conserved.
Unit 4: Fields and Options FAQs
What does WJEC A Level Physics Unit 4: Fields and Options cover?
Capacitance, electrostatic and gravitational fields, orbits and the wider universe, magnetic fields, electromagnetic induction and one option.
Which option should I revise for Unit 4?
Only the option your centre has taught: Alternating Currents, Medical Physics, The Physics of Sports, or Energy and the Environment.
How do I compare electric and gravitational fields?
Make a side by side table of force, field strength and potential equations, noting that both are inverse square, but gravity is always attractive while electric forces can repel.
